Amtrol EX-15 Extrol Expansion Tank — 2 Gal for Closed Hydronic Heating & Cooling

Overview

The Amtrol EX-15 Extrol expansion tank is a compact diaphragm-style reservoir designed for closed hydronic heating and cooling loops. Patented in 1954, Extrol helped popularize easier pressure control and steadier water flow in a wide range of radiant, boiler, and packaged system configurations.

Key benefits at a glance

• 2 gallon capacity provides a compact buffer to absorb volume changes
• Not intended for potable water; ideal for sealed heating and cooling circuits
• Factory precharge of 12 psig supports quick setup on many systems
• Max working pressure of 100 psig and max operating temperature of 240°F for robust operation
• Watertight reservoir and thick Butyl/EPDM diaphragm aimed at long service life

How it works in real life

As a closed-loop system heats and cools, the tank accepts expanded water, helping stabilize pressure and smooth pump cycling. The result can be more comfortable temperature swings and quieter operation in scenarios like radiant floor heating or packaged boiler loops.

Because it’s a dedicated expansion solution, it can contribute to system reliability by buffering pressure peaks that occur when boilers start or valves close.

Specifications at a glance

• Capacity: 2 gallons (EX-30 is the larger model)
• Precharge: 12 psig
• Max working pressure: 100 psig
• Max operating temperature: 240°F
• Construction: watertight reservoir with thick diaphragm
• Application: closed hydronic heating and cooling systems only

Durability and reliability

Durability and reliability come from a thick Butyl/EPDM diaphragm that resists aging and maintains elasticity across temperature swings, while a robust reservoir keeps expanded water sealed away from the rest of the system. The 2-gallon size is ideal for tight spaces, offering a balance between buffering capacity and footprint.

Installation and care tips

• Use only in non-potable, closed systems per local codes
• Verify precharge is matched to system design if required
• Inspect for leaks and ensure proper mounting to prevent vibration

Note: This tank is part of a long‑standing family of Extrol products known for dependable pressure control in many types of hydronic plumbing. Results depend on the overall system design and operating conditions.